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D1492-21 – Standard Test Method Technical Guide
The ASTM D1492-21 standard establishes a coulometric titration test method for determining the Bromine Index in aromatic hydrocarbons, their derivatives, and related chemicals. This method is critical for detecting low levels of unsaturated impurities, with a defined scope covering samples up to a Bromine Index of 100.
📐 Test Method Scope and Principle
This test method is specifically designed for determining the Bromine Index, defined as the number of milligrams of bromine consumed by 100 g of sample (mg-Br/100 g) under specified conditions. The analytical procedure relies on adding a specimen to a prepared solvent and titrating it with electrolytically generated bromine at room temperature. The precise quantification of consumed bromine is achieved through coulometric titration. All values are reported in SI units, which are regarded as the standard for the method.
The standard is applicable to a wide range of aromatic hydrocarbon samples and their derivatives, providing a highly sensitive measure of trace unsaturation.
⚙️ Procedure and Performance Characteristics
The performance of the coulometric titration method in D1492-21 is rigorously defined by specific detection and quantitation limits. These metrics ensure the method’s suitability for ultra-low level analysis.
| 🔍 Parameter | 📏 Specified Value | ⚡ Units / Notes |
|---|---|---|
| Applicable Concentration Range | Up to 100 | Bromine Index |
| Limit of Detection (LOD) | 1.5 | Bromine Index |
| Limit of Quantitation (LOQ) | 4.9 | Bromine Index |
| Titration Environment | Room Temperature | Electrolytically Generated Bromine |
💡 Technical Note: The Limit of Detection (LOD) of 1.5 and the Limit of Quantitation (LOQ) of 4.9 Bromine Index were calculated using data from the D16 Proficiency Testing Program (PTP). This estimate of the LOD specifically incorporates within-laboratory variability.
⚠️ Safety Warning: This standard does not purport to address all safety concerns. Users must establish appropriate safety, health, and environmental practices. Specific hazard statements are detailed in Section 8 of the standard. Compliance with relevant OSHA regulations (29 CFR 1910.1000 and 1910.1200) is recommended.
📊 Referenced Standards and Quality Assurance
D1492-21 is part of a comprehensive framework of companion ASTM standards. Interlaboratory precision is determined according to Practice E691, and the rounding of test results for conformance to specifications must follow the rules in Practice E29. The table below details key companion standards critical to the method.
| 📜 Reference Standard | 🎯 Role in Testing |
|---|---|
| D5776 | Alternative test method for Bromine Index using Electrometric Titration |
| D6809 | Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons |
| D1193 | Specification for Reagent Water used in the test procedure |
| E29 | Practice for Using Significant Digits to Determine Conformance with Specifications |
❓ Frequently Asked Questions
🔍 What is the definition of Bromine Index (B)?
Bromine Index is formally defined as the number of milligrams (mg) of bromine consumed by 100 g of sample under the specific conditions of the test. It is reported as mg-Br/100 g of sample.
💡 What are the detection and quantitation limits of D1492-21?
This standard rigorously establishes a Limit of Detection (LOD) of 1.5 Bromine Index and a Limit of Quantitation (LOQ) of 4.9 Bromine Index. The method is validated for samples with concentrations up to 100 Bromine Index.
⚡ How does D1492 differ from the related standard D5776?
Both methods determine Bromine Index. D1492 utilizes coulometric titration with electrolytically generated bromine, which is particularly suitable for achieving the very low LOD and LOQ values. D5776 employs an electrometric titration technique. The choice of method depends on the specific application and sample type.
📌 How should results be rounded for compliance?
Per the standard’s guidelines for determining conformance to specifications, test results shall be rounded off in accordance with the rounding-off method described in Practice E29.